Parents Do It -- Often!

Wikipedia, http://en.wikipedia.org/wiki/Types_of_rape#Rape_of_children:

Psychologists estimate that 40 million adults, 15 million of those being men (Adams 1991), in the United States were sexually abused in childhood often by parents, close relatives and other elders on whom they were dependent. According to the National Center for Victims of Crime 46% of rape committed in the United States is perpetrated by a family member.

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The dynamic evidence page

It's here: the law of evidence on Spindle Law. See also this post and this post.